Sniper skills are in demand in current US military operations. Although sniper weapons have the capability to shoot at ranges beyond 1 km, wind effects on bullet trajectories degrade the performance of sniper systems, particularly at ranges of 300 m or more. Spotters and snipers estimate winds largely by visual observations, and then adjust weapon sights and the shooter's point of aim. Accurate crosswind estimation is the biggest single factor in achieving first round hits at very long ranges; this manual process is especially challenging in windy conditions, in poor visibility, or at night.
Various detectors are available for remote detection of wind speed. These include detectors based on Doppler principals using light or acoustic reflections from particles flowing with the wind detected with a sensor. But these detectors are limited to detection of wind speed along the axis of the sensor. Measurements of crosswinds are more complicated. An approach for measuring path-integrated crosswind based on laser beam degradation phenomenon called scintillation was suggested in M. S. Belen'kii, “The Effect of Residual Turbulent Scintillation and Remote Sensing Technique for Simultaneous Determination of Turbulent and Scattering Parameters of the Atmosphere,”, J. Opt. Soc. Amer. A Vol. 11, No. 3, pp. 1150-1158 (1994). That device collected reflected light from a laser beam directed at a retro-reflecting target. The reflected light is detected by two separated detectors (each with a number of fields of view) which monitored turbulent scintillation effects. Wind speed can be determined by time differences between the passages of dark fringes across various fields of view. With this device using the retro-reflector a small inexpensive HeNe laser could be used. This method was experimentally demonstrated as described in M. S. Belen'kii, G. G. Gimmestad, and D. W. Roberts, “Single-ended Laser Wind Sensor,” In Image Propagation Through the Atmosphere, Proceeding SPIE, Vol. 2828, 489-494 (1996) using a 4 mW He—Ne laser in a controlled, laboratory environment and also outdoors. The laser wind sensor was found to be more sensitive than the mechanical anemometer. It recorded air motion within the range of ±0.25 m/s. This method can be modified for measuring the crosswind profile along the propagation path by using the concept of a cross-path LIDAR technique described in M. Belen'kii, et. al., “Optical Methods for Turbulence Profile Determination” Final Report, AFRL, 2005. However, such an approach similar to previously suggested active crosswind sniper systems has a fundamental shortcoming. It requires the transmission of two laser beams in the atmosphere. This greatly increases complexity of the sniper system, as well as power consumption, size, weight, and cost. In addition, it can jeopardize the covertness of the sniper operation.
There are many important applications for a good low-cost, light weight crosswind profiler. An important application is for use in crosswind correction for telescopic aiming devices for military rifles.
What is needed is a small, light weight passive crosswind profiler.